Orthogonal frequency division multiplexing (OFDM) has been adopted as the main transmission waveform of many advanced wireless communications systems, including the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE). OFDM offers many benefits including: efficient implementation using Fast Fourier Transforms (FFT), robustness against multipath fading channel when used in conjunction with a cyclic prefix (CP), and the like.
A drawback of OFDM is that it has high spectral side lobes, which makes it spectrally inefficient due to the necessity of a frequency guard band. As an example, in 3GPP LTE, the frequency guard bands account for approximately 10% of the available bandwidth. Therefore, a significant fraction of the available bandwidth is not being used to improve communications system performance.